Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
  • C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
  • C09D127/12—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C09D127/16—Homopolymers or copolymers of vinylidene fluoride
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F114/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
  • C08F114/18—Monomers containing fluorine
  • C08F114/22—Vinylidene fluoride
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
  • C08F14/18—Monomers containing fluorine
  • C08F14/22—Vinylidene fluoride

Definitions

• the present invention relates to a process for the manufacture of vinylidene fluoride polymers, and to to the use of the resulting vinylidene fluoride polymers for the formulation of paints and, more particularly, of paints intended for prelacquering metal sheets.
• French Patent FR-A-2,056,636 in the name of sud Weg Kalkstickstoff-Werke AG, describes a process for the manufacture of polyvinylidene fluoride as fine (primary) particles with a mean size of approximately 0.2 microns, suitable for the formulation of organosol varnishes intended for the protection of metals.
• the process in question consists in polymerizing vinylidene fluoride in aqueous medium, in the absence of an emulsifying agent, with the use of peroxydisulphates as initiators. This process is particularly attractive because of its simplicity and of the small number of polymerization ingredients needed for its use (essentially water, monomer and water-soluble initiator).
• the aim of the present invention is to provide an improved process for the manufacture of vinylidene fluoride polymers which can be employed for the formulation of paints with improved gloss.
• the present invention relates to a process for the manufacture of vinylidene fluoride polymers by noncontinuous polymerization of vinylidene fluoride in aqueous media with the use of peroxydisulphates as initiators and in the absence of emulsifying agent, characterized in that a chain-control agent is introduced into the initial aqueous charge intended for the polymerization, the said chain-control agent being chosen from alkyl acetates whose alkyl groups contain 1 to 3 carbon atoms.
• alkyl acetates which can be employed in the process of the invention there may be mentioned methyl, ethyl, propyl and isopropyl acetates.
• a very particularly preferred alkyl acetate is ethyl acetate.
• the quantity of chain-control agent to be used is not particularly critical. It depends, of course, on the molecular weight and therefore on the intrinsic viscosity which it is intended to impart to the polymer. In general, from approximately 0.5 to 3% by weight of control agent is employed relative to the monomer used. Within this concentration range, the quantity of control agent will be advantageously chosen by experiment as a function of th polymerization conditions and of the intended result. A generally preferred concentration range runs from 1 to 2% of control agent relative to the monomer used. In this concentration range, polyvinylidene fluorides are produced whose intrinsic viscosities, measured in dimethylformamide at 25° C, are between approximately 0.12 and 0.005 g/1.
• the polymerization is initiated by initiators of the peroxydisulphate type.
• peroxydisulphates there may be mentioned peroxydisulphates of alkali metals such as sodium and potassium, and ammonium peroxydisulphate. Ammonium peroxydisulphate is preferably employed.
• the quantity of initiator used in the polymerization can vary within certain limits. It is nevertheless advisable to employ at least 0.005 g/1 of aqueous phase and not more than 0.5 g/1 of aqueous phase.
• the initiator concentration is preferably between approximately 0.03 and 0.2 g/1 of aqueous phase.
• the initiator may be present wholly or partially in the initial aqueous charge. According to a preferred embodiment of the invention all the peroxydisulphate is introduced progressively into the charge in the course of polymerization.
• the polymerization temperature is not critical. Nevertheless, it lies advantageously in the range approximately from 80 to 95° C.
• vinylidene fluoride is above its critical temperature (30.1° C.), so that the operating pressure depends essentially on the temperature and on the quantity of monomer present in the polymerization vessel.
• the polymerization pressure lies advantageously above 20 bars and preferably approximately between 30 and 45 bars. It is controlled and maintained by the progressive introduction of vinylidene fluoride.
• the total quantity of vinylidene fluoride introduced does not generally exceed 0.22 parts per 1 part by weight of water.
• a preferred embodiment of the process of the invention consists, therefore, in introducing all the chain-control agent (alkyl acetate) into the initial aqueous charge intended for the polymerization and in introducing the initiator and vinylidene fluoride progressively into the charge in the course of polymerization, the latter compound being introduced in a sufficient quantity to maintain the pressure at the chosen value.
• chain-control agent alkyl acetate
• Vinylidene fluoride polymerization is intended within the scope of the present invention to denote the homopolymerization of vinylidene fluoride and the copolymerization of mixtures of monomers with a preponderance, preferably more than 85 mol%, of vinylidene fluoride, such as, for example, mixtures of vinylidene fluoride with other fluoroolefins, such as vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene and hexafluoropropylene. Nevertheless, preference is given to the homopolymerization of vinylidene fluoride.
• the process according to the invention results in aqueous dispersions of finely divided vinylidene fluoride polymers whose primary particles, uniformly spherical, exhibit a mean size of approximately 0.1 to 0.3 microns.
• the vinylidene fluoride polymers obtained according to the process of the invention are isolated from the polymerization medium in the usual manner and, in particular, by coagulation, filtration, washing and drying.
• the coagulates are milled, during or after drying, so as to obtain vinylidene fluoride polymers as particles whose mean size is below 20 microns.
• the vinylidene fluoride polymers obtained according to the process of the present invention are very particularly suitable for the formulation of gloss paints.
• the use of these polymers for the formulation of paints consequently forms another aspect of the present invention and, in particular, for the formulation of paints intended for the prelacquering of metal sheets.
• formulations of paints based on polyvinylidene fluoride usually include a resin, such as an acrylic resin, which is compatible with polyvinylidene fluoride and more soluble than polyvinylidene fluoride in the said solvents, and intended to improve its dispersion in the paint, as well as pigments and surface-active agents.
• a resin such as an acrylic resin, which is compatible with polyvinylidene fluoride and more soluble than polyvinylidene fluoride in the said solvents, and intended to improve its dispersion in the paint, as well as pigments and surface-active agents.
• Examples 1 to 3 illustrate the use of ethyl acetate as a chain-control agent.
• Example 4 illustrates the process of the prior art (without chain-control agent).
• the polymerization is stopped by interrupting the injection of vinylidene fluoride and of catalyst, and the heating is then turned off and the autoclave is degassed.
• the latex (approximately 0.2-micron primary particles) is coagulated with sodium chloride, filtered, washed and dried at 60° C. 5.5 kg of polyvinylidene fluoride are recovered. The coagulate is milled so as to obtain a polymer whose mean particle size is below 20 microns.
• the intrinsic viscosities, measured in dimethylformamide at 25° C., of the polyvinylidene fluorides obtained according to Examples 1 to 3 are recorded in Table I, attached.
• the white paint formulated as above is applied onto a 0.6 mm thick aluminium panel.
• a coat of phenoxy resin-based primer paint is applied first of all at a dry film thickness of approximately 5 microns and the phenoxy coating is cured by placing the panel in an oven so as to reach a temperature of 232° C. over a period of time not exceeding a minute (29 s in this case). The panel is then withdrawn from the oven and immediately plunged into a cold water bath.
• the white paint is applied by means of a wire spreader so as to obtain a dry film thickness of 20 microns and the paint is crosslinked by placing the panel in an oven so as to attain a temperature of 254° C. over a period of time not exceeding a minute (34 s in this case).
• the panel is withdrawn from the oven and cooled in a water bath before being dried.
• the gloss of the white paints is measured by means of a specular glossmeter in accordance with ISO standard 2813-1978, the angle of incidence of the light beam being equal to 60°.
• the principle of this evaluation consists in measuring the ratio of the luminous flux reflected by the sample at an angle of 60° to the luminous flux reflected by a polished black glass (refractive index 1.567) to which a gloss of 100 is assigned.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Paints Or Removers (AREA)
• Polymerisation Methods In General (AREA)
• Polymerization Catalysts (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (16)

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Citations (14)

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• 1989
  • 1989-03-15 FR FR8903497A patent/FR2644466B1/fr not_active Expired - Fee Related
• 1990
  • 1990-03-05 EP EP90200515A patent/EP0387938B1/de not_active Expired - Lifetime
  • 1990-03-05 DE DE90200515T patent/DE69003283D1/de not_active Expired - Lifetime
  • 1990-03-05 AT AT90200515T patent/ATE94566T1/de not_active IP Right Cessation
  • 1990-03-07 US US07/489,493 patent/US5095081A/en not_active Expired - Fee Related
  • 1990-03-15 JP JP2065514A patent/JPH0328206A/ja active Pending

Patent Citations (15)

Non-Patent Citations (2)

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